1. Field of the Invention
The present invention relates to a semiconductor device, a driving method of the semiconductor device, and the like. The present invention particularly relates to a circuit for a display device.
Note that in this specification, a semiconductor device means a circuit including a semiconductor element (e.g., a transistor or a diode) and a device including the circuit. The semiconductor device also means any device that can function by utilizing semiconductor characteristics. For example, an integrated circuit, a chip having an integrated circuit, a display device, a light-emitting device, a lighting device, and an electronic device are all semiconductor devices.
2. Description of the Related Art
A screen of an active matrix display device includes a plurality of pixels arranged in an array. The pixels are each configured with a circuit. The pixel circuits in the same row are connected to a gate line in that row, and the pixel circuits in the same column are connected to a source line in that column. The pixel circuit is provided with a switch which controls an on or off state by a gate signal input to the gate line. Pulse signals are sequentially supplied to the gate lines arranged in a vertical direction from a gate driver, so that pixels are selected row by row. To the pixel circuits of the selected row, a source signal corresponding to an image signal is input from a source line.
Further, as one of means of downsizing, weight saving, and obtaining narrowed frame of an active matrix display device, it has been known to form a gate driver and a pixel portion on one substrate. Pixel circuits of the display device can be formed with either an n-channel transistor or a p-channel transistor. However, it is preferable to design a gate driver with a single conductivity type transistor instead of using a CMOS circuit in order to manufacture a display device having a narrow bezel width with reduced number of manufacturing steps and manufacturing cost.
Main circuits of the gate driver are shift registers. For example, Patent documents 1 and 2 each disclose a shift register including single conductivity type transistors. Patent document 1 discloses a gate driver in which a demultiplexer is connected to an output terminal of a shift register. Patent document 2 discloses a gate driver capable of partial driving by which data displayed on the screen is partly rewritten.